The Research On Hydrolysis Of Cellulose With Coal-Based Solid Acid Bearing Chlorine

Cellulose,which is a linear polymer formed by the repeating connection of D-glucose units through ?-1,4-glycosidic linkages,is considered to be an abundant,widespread and inexhaustible raw material.The traditional hydrolysis method is mainly liquid acid and enzyme hydrolysis,but their practical applications are limited due to a lot of problems including reactor corrosion,difficult separation of products and high cost.In order to overcome the above-mentioned drawbacks,the carbon-based solid acid has been efficiently used in the cellulose hydrolysis in recent years.The structure of coal is similar to the carbon-based solid acid except-SO3 H,which means coal has the genetic advantage of preparing carbon-based solid acid.A novel coal-based solid acid was prepared by introducing chlorine of the stronger electronegativity into the aromatic carbon sheets of conventional carbon-based solid acid from coal,which could break the intramolecular hydrogen-bonding network and promote the activity of cellulose hydrolysis.In this paper,several various coal-based solid acids were prepared by changing the caking coal,chlorination method,chlorination agent,which were applied in the cellulose hydrolysis.The structure of coal-based solid acids was characterized by SEM,Raman Specturm,BET,XRD,FT-IR,XPS and the catalytic performance of coal-based solid acids was evaluated by the density of functional groups,absorbed amounts and yield of reducing sugar.We studied the hydrolysis mechanism in order to realize the effective integration of different reactive functional groups.Four kinds of coal-based solid acids were prepared by sulfonation of cocarbonizaed different caking coal and trichloroacetic acid?TDA?,and the relationship among the chemical composition of carbon resource,catalyst structure and the activity of cellulose hydrolysis.The results showed that the aromatic carbon sheets of coal-based solid acids synthesized from high caking coal were more flexible and disordered,the densities of-COOH and total acid of catalyst were higher,and the adsorption capacity and hydrolytic activity of CCSA were also better.Three kinds of coal-based solid acids were prepared from high caking coal?JKFM?as the starting materials by different chlorination methods.The results showed that the new generated Cl groups were covalently bonded to aromatic carbon sheets and the chemical combination states of sulfur were oxidation state?-C-SO_x-?and non-oxidation state?C-S-C?,respectively.The aromatic carbon sheets of coal-based solid acid?SH-SO₃H?synthesized were less flexible and ordered,the degree of aromatic ring condensation was bigger,the density of-SO3 H was lower,but the density of-Cl was the largest,and the adsorption capacity and hydrolytic activity were the best.Three kinds of coal-based solid acids were prepared by sulfonation of cocarbonization JKFM and different chlorination agents.The results showed that the reaction takes place during the cocarbonization process,chlorine atom is introduced into the aromatic carbon sheets and the uniform distribution of carbon,oxygen,sulfur and chlorine was detected.The aromatic carbon sheets of coal-based solid acids prepared by chlorination were less flexible and ordered,the aromatic degree and lateral size become bigger.The density of-Cl groups was affected greatly by the different chlorination agents,which of coal-based solid acid prepared using trichloroacetic acid as chlorination agent reached maximum,and the adsorption capacity and hydrolytic activity were the best.We investigated the effect of chlorination agent proportion on the structure and catalytic performance of coal-based solid acids.The results showed that the added amount of TDA had a great effect on the densities of active functional groups.With the increase of the ratio of coal to TDA,the density of-SO3 H and-COOH increased,while the density of-SO3 H groups decreased.The cellobiose adsorbed on catalysts exhibited an increasing tendency with the addition of chlorinating agent,indicating that the presence of chlorine was beneficial to improve the adsorption capacity.